Solubility of Ionic Solids in Polar And Non-polar Solvents

Hello guys, in this article we will discuss about the solubility of ionic solids in polar and non-polar solvents. Hopefully you'll find your answer and understand the concept. 

A given ionic solid is soluble or insoluble is depend on two factors. 

1. Lattice energy 
2. Hydration energy 

• Lattice energy :-

It tends to oppose the dissolution of ionic solid into it's cations and anions.

Higher the lattice energy, lesser is the solubility of ionic solid.

• Hydration energy :-

It is the energy liberated when a cation or anion hydrolysed by the water molecules. So basically it tends to dissolve the ionic solid.

Higher the hydration energy, higher is the solubility of ionic solid.

NOTE:-

When a solvent other than water is used then, hydration energy is better called as solvation energy.

Now we move to the solubility concept-

Solubility of ionic solids in non-polar solvents:-

Ionic solids are insoluble in non-polar solvents. Let's understand the reason behind it. 

Reason:- Ionic solids are insoluble in non-polar solvents because the cations and anions do not interact with non-polar solvent molecules and so no solvation energy is produced.

On the other hand lattice energy tends to oppose the dissolution of solid.

Solubility of ionic solids in polar solvents:-

In polar solvents solvent molecules well interect with ionic solids and so a considerable amount of solvation energy(or hydration energy in case of water) is produced. So these solids are soluble in polar solvents.

Altough the solubily of ionic solids in polar solvents depends on various factors. Such as size of cation and anion, charges on both the ions, type of ion and dipole moment of the solvent.

Let's understand these factors with the help of examples-

Example-1:-

Halides of Lithium metal; LiF, LiCl, LiBr, LiI.

Since all halides have same charge of -1, so their solubility will be depend on size of halide ion.

Order for size of halide ions is:- I⁻ > Br⁻ > Cl⁻ > F⁻

Also the lattice energy is inversely proposnal to size of ion. And as i said before higher the lattice energy lower will be the solubility.

Order for lattice energies of halides of Li metal is:- LiI < LiBr < LiCl < LiF

So order for solubility of halides of Li metal is:- LiI > LiBr > LiCl > LiF

Example-2:-

Comparision of solubility of K₂CO₃ and CaCO₃.

In both the compounds CO₃²⁻ ion is same while cations K⁺ and Ca²⁺ have different charges.

Also the lattice energy is directly proporsanal to charge of ions.

So the order for lattice energies is :- CaCO₃ > K₂CO₃

Hence order for solubility is:- K₂CO₃ > CaCO₃

Thank you guys for reading my article, hoping your doubts are clear now. You may also cheak my other articles on chemistry. See you soon.